Crossword Puzzle for
Classification of Living Things
Topics 4-5: Class and Infraclass to Subclass

Across

2. The ability of reptiles,
amphibians, fish, and insects to
maintain their core body
temperature in a normal range
mainly by avoiding exposure to
environmental temperature
extremes. This is also referred
to as being cold blooded.6. The infraclass of therian mammal
species in which females give
birth to their young in an
immature condition (while still in
the early fetal stage) and then
permit their further infant
development in an abdominal pouch
covering their mammary glands.
They are also called marsupials.
Included in this infraclass are
kangaroos, koalas, and opossums.7. The class of vertebrates that
includes the jawless fish that do
not have scales. These are the
lampreys and hagfish.10. A kind of egg which usually has a
hard shell that protects the
embryo from drying out. This is
an advantage because it can be
laid on land where it is usually
safer from predators than it would
be in lakes, rivers, and oceans.
These eggs are produced by
reptiles, birds, and some
primitive mammals.12. The class of vertebrates that
include the fish that have
skeletons consisting of bone.
Most fish species are in this
class (e.g., tuna, bass, perch,
salmon, trout, etc.).13. The subclass of mammals that
include the marsupials and
placental mammals. They have in
common the fact that they give
birth to live young instead of
laying eggs.15. The milk secreting glands of
mammals. They are usually located
on the chest or abdomen in one or
more bilaterally symmetrical pairs. They are also referred to
as breasts.16. The class of vertebrates that
includes the fish that have
skeletons consisting of firm
rubber-like cartilage rather than
bone. These are the sharks and
rays.

Down

1. The class of warm blooded, usually
hairy animals, that feed their
young with milk produced by
mothers. This class includes
monotremes, marsupials, primates,
cats, dogs, bears, hoofed animals,
rodents, bats, seals, dolphins,
and whales.3. The class of vertebrates that
includes turtles, snakes, lizards,
alligators, and dinosaurs. They
all have lungs to breathe on land
and skin that does not need to be
kept wet.4. The term referring to the
characteristic of having a variety
of specialized teeth. Mammals
have this characteristic but the
other classes of vertebrates do
not.5. The subclass of mammal species in
which females lay eggs like non-
mammalian vertebrates. However,
they feed their newborn with
mammary gland secretions like all
other mammals. They are also
referred to as monotremes, which
literally means that they have one
opening for excretion and
reproduction. Included in this
subclass are the platypus and
echidna.8. The vertebrate class that includes
animals that spend part of their
lives under water and part on
land. All of these animals must
return to damp areas to reproduce
since their eggs would dry out
otherwise. They start life with
gills, like fish, and later
develop lungs to breath air.9. The ability of birds and mammals
to maintain a relatively constant
core body temperature regardless
of external conditions by using
internal physiological means.
That is to say, they are
homeothermic or stable in core
body temperature. This is also
referred to as being warm blooded.11. The infraclass of therian mammal
species in which females produce a
placenta to connect the fetus to
the uterus. This enables
nutrients and oxygen to get to the
fetus and provides a means of
eliminating waste products. As a
result, these mammals can carry
their young within the uterus
until late in fetal development.
This has a selective advantage
because it results in decreased
infant mortality. They are also
called placental mammals.
Included in this infraclass are
dogs, cats, bears, whales, and
primates.14. The vertebrate class that includes
animals that have wings and can
produce amniote eggs. In the case
of both reptiles and these
creatures, the eggs are fertilized
within the reproductive tract of
females.